How to build a bookcase around a window

The exact dimensions of your window seat bookcase will depend on the size and placement of the window in your wall.

The structure starts with a 2-by-4 frame that will form the toe kick for the unit. The frame is 15 inches wide and runs the length of the wall. It is nailed to the wall and the floor to secure it.

We use ¾-inch cabinet-grade plywood to create the window seat.

The seat will be 18 inches deep so we’re cutting the top and bottom to that dimension. From the remainder of the sheet, we cut five 18-inch by 12-inch pieces that will act as dividers and vertical supports.

We nail those pieces together to form a long, open-ended box divided into four equally spaced smaller boxes.

This box goes on top of the toe kick and is nailed to it and to the studs in the surrounding walls.

The bookcase portion of our unit is made by 1-by-12 pre-primed shelf boards.

We need four vertical supports of identical length — two on either side of the window — that will run from the top of the window seat to just above the window.

Next, we mark the shelf locations on one of these and transfer the marks to the other three so all the shelves line up.

Then we nail together the two different shelf units — one for either side of the window.

Next, we position them on top of the window seat, check their level, and nail them to the adjacent walls.

We’ve left the top of the shelf units open and join them with one long shelf that spans both units.

Once it’s nailed in place, the basic structure is complete.

The last step is adding 1-by-2 facing to all forward-facing edges. This hides the edge grain on the plywood window seat and adds strength and dimension to the 1-by-12 shelves.